Sunday, November 10, 2019

2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 2731

2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 2731

Diagnostic Aids

* Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no

associated "current" or "active" status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are

transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically

after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:

- A control module on the data communication circuit was disconnected while the communication circuit is awake.

- Power to one or more control modules was interrupted during diagnosis.

- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.

- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.

- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above.

These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.

* A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between

control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a

control module based only on a history U-code.

* Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication

issue.

* Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system

inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.

* Use Data Link References (See: Powertrain Management/Computers and Control Systems/Information Bus/Testing and Inspection/Initial

Inspection and Diagnostic Overview) to determine if the control module uses high or low speed GMLAN serial data communications.

* Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and

the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control

module.

* This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to,

providing the vehicle is equipped with the control module.

Reference Information

Schematic Reference

* Data Communication Schematics (See: Powertrain Management/Computers and Control Systems/Information Bus/Diagrams/Electrical

Diagrams)

* Control Module References (See: Testing and Inspection/Programming and Relearning)

Connector End View Reference

Component Connector End Views (See: Diagrams/Connector Views)

Description and Operation

Data Link Communications Description and Operation (See: Powertrain Management/Computers and Control Systems/Information

Bus/Description and Operation)

Electrical Information Reference

* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit

Testing/Circuit Testing)

* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic

Procedures/Connector Repairs/Connector Repairs)

* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General

Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)

* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring

Repairs/Wiring Repairs)

Scan Tool Reference

Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information

Circuit/System Verification

Verify that DTC U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.

If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic

Trouble Code (DTC) List - Vehicle).

Circuit/System Testing

Note: Use the schematic to identify the following:

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